1. Field of the Invention
The present invention relates to a battery management system of a vehicle, and more particularly, to a battery management system that prevents a lithium battery from being overcharged and over-discharged and that safely protects the lithium battery from various conditions that may degrade the lithium battery when the lithium battery is used as a low-voltage battery in the vehicle.
2. Description of the Related Art
An electric vehicle or a fuel cell vehicle as an eco-friendly vehicle includes a low-voltage battery (which is also referred to as a “supplementary battery”) for providing power required to turn on a vehicle and providing power to electric field loads operating at a low voltage. In addition, a general internal combustion engine vehicle for driving an engine using fossil fuel also includes a rechargeable battery for providing power required to turn on a vehicle or providing power to electric field loads. As such a battery, a lead acid battery to be manufactured with low price has been used thus far but it is predicted to use a lithium battery with a longer lifespan and improved electrical characteristics as a substitute.
A lithium battery requires complete charging due to the characteristics thereof and, thus, when a charging state of a supplementary battery decreases to less than a preset threshold voltage (e.g., discharge lower voltage limit), the lithium battery is installed to shut off electrical connection with a vehicle system using a relay. To restart a vehicle while electrical connection is shut off by a relay, the relay is manually turned on to form electrical connection again. In this regard, typically, a reconnection switch configured to apply a battery voltage directly to a coil of the relay is used. In other words, typically, when a user pushes the reconnection switch, the relay is turned on to electrically connect the battery to a vehicle system as the battery voltage is applied to the coil for driving the relay.
Such a typical battery relay reconnection method has various problems. For example, when a reconnection switch is maintained in an on-state for a predetermined time period or more due to a maloperation of the reconnection switch and the like, a problem arises in that the relay coil is damaged since a battery voltage is continuously applied to a relay coil. In addition, a problem arises in that the battery is over-discharged since the battery relay is maintained in an on-state for a long period of time during an in-line operation. Further, a problem arises in that the battery is overcharged or an overvoltage is applied to rapidly degrade the battery when external power is connected to a terminal of a vehicle of the relay for jump-starting, when an external power source has a voltage of a predetermined level or greater.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.